A Unusual Case in Cardiac Anatomy

The deceased: A 39-year-old man in the United States.

The autopsy findings: Medical examiners looked into the man’s cause of death following a fatal altercation, where he suffered a stab wound that damaged a vein in his lungs. They observed that his heart was somewhat enlarged and showed signs of moderate atherosclerotic coronary artery disease (CAD) in two arteries. CAD occurs due to a buildup of plaque within the artery walls that supply the heart.

While examining the heart, they discovered an unexpected lump around the atrioventricular node, which is critical for regulating electrical signals in the heart. When the investigators prepared the surrounding tissue for closer inspection, they found a unique “boomerang-shaped, bony structure” roughly the size of a black bean, according to a case report.

This structure was identified as the os cordis — a rare “cardiac bone” that is scarcely found in humans.

What makes the case unique: The os cordis has been documented in various nonhuman mammals, especially ruminants like cows and camels, where it’s thought to reinforce the cardiac valves that manage blood flow within the heart.

It was only recently noted in primates in a report published in 2020. In that study, researchers looked at 16 chimpanzee hearts and noted that three of them had an os cordis. Interestingly, those chimps also exhibited scarring in heart tissue, leading scientists to consider that this bone-like structure might develop due to such tissue damage.

In the same year, another study reported a similar finding in seven humans by Dr. Jorge Trainini, a cardiac surgeon from Argentina. He referred to what they discovered as the “cardiac fulcrum,” suggesting it plays a role in stabilizing heart muscles against gravitational forces. However, they pointed out that, unlike the os cordis seen in animals, the human structure was primarily made of cartilage and tendon.

Trainini indicated in an interview that he believes the os cordis and the cardiac fulcrum refer to the same structure. However, the authors of the case report disagreed, claiming that their findings were distinct due to its bony composition.

Despite these differing perspectives, both parties seem to agree that such structures may be more prevalent in humans than currently acknowledged. The case report authors hypothesized that the os cordis might often go undetected since it was discovered during a dissection conducted outside the standard protocols of an autopsy.

Furthermore, Trainini suggested that, based on his studies of approximately 100 human hearts, most humans likely possess a cardiac fulcrum.

While the full medical history of the deceased man is unknown, the authors noted the possible link between the os cordis formation and his evident coronary issues, which align with findings in other species, where age and disease can influence the presence of such structures.